Effect of organic chelates on the performance of hybrid sol–gel coated AA 2024-T3 aluminium alloys |
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Authors: | PC Rajath Varma John Colreavy John Cassidy Mohamed Oubaha Brendan Duffy Colette McDonagh |
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Affiliation: | aCentre for Research in Engineering Surface Technology (CREST), FOCAS Institute, Dublin Institute of Technology, 13 Camden Row, Dublin 8, Ireland;bSchool of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin 8, Ireland;cNational Centre for Sensor Research (NCSR), Dublin City University, Dublin 9, Ireland |
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Abstract: | Sol–gels are organic–inorganic polymers formed by hydrolysis/condensation reactions of alkoxide precursors, primarily silanes, which have found applications as electronic, optical and protective coatings. These coatings possess important characteristics such as chemical stability, physical strength and scratch resistance. Further performance improvement is achieved through the incorporation of zirconium and titanium based nanoparticles, also formed through the sol–gel process. However due to the inherent difference in the reactivity of the precursors, the hydrolysis of each precursor must be carried out separately before being combined for final condensation. Zirconium precursors are commonly chelated using acetic acids, prior to hydrolysis, to lower the hydrolysis rate.In this body of work various ligands such as organic acids, acetyl acetone (AcAc) and 2,2′-bipyridine (Bipy) were used to control the zirconium hydrolysis reaction and form nanoparticles within the silane sol matrix.Nanoparticle modified coatings formed from the silane sol on AA 2024-T3 aluminium were characterised spectroscopically, electrochemically and calorimetrically to evaluate the potential effect of the different chelates on the final film properties while neutral salt spray tests were performed to study their anti-corrosion performance. Results indicate that the acid ligand modified coatings provided the best performance followed by AcAc, while Bipy was the poorest. In all cases the zirconium nanoparticle improved the protective properties of the sol–gel coating. |
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Keywords: | Ormosil Zirconium Chelate Coating Nanoparticles |
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